In an electrophotographic apparatus such as a copying machine, a printing machine and the like, an organic photoconductor (OPC) which is sensitive to irradiation of a light sauce mounted on the apparatus, have been widely employed. An OPC is generally classified as that of mono-layered construction and of bi-layered construction. A mono-layered OPC is the one which has a mono-layered photoconductive layer composed of a resinous matrix and a charge generating material and a charge transporting material dispersed in the resinous matrix. A bi-layered OPC is the one which has a bi-layered photoconductive layer composed of a charge generating layer and a charge transporting layer laid thereon. The charge generating layer comprises a resinous matrix and a charge generating material dispersed therein. The charge transporting layer comprises a resinous matrix and a charge transporting material dispersed therein.
An organic photoconductive substance which is sensitive to irradiation wavelength region of semi-conductor laser (about 800 nm), has been a matter of interest in the art as a charge generating material.
A lot of OPC employing such an organic photoconductive substance as an active ingredient, have also been proposed. Examples thereof include an OPC which contains a titanyl phthalocyanine compound as a charge generating material.
In recent years, dezitization and speeding up of a copying machine, or a printing machine is progressing. Thus, with respect to the OPC which is for use in an electrophotographic apparatus such as a copying machine, a printing machine and the like, improvement of photoresponse, stability, and durability are strongly desired.
Phthalocyanine (This is hereinafter referred to as "Pc".) shows wide variety of electronic properties depending on a kind of the central metal atom bonded thereto, on a kind of the peripheral substituent, and on a kind of preparing process or treating process. It is also known to the art that even if the chemical structure of Pc is equal, when stacking state of the molecules of Pc is different, electronic properties thereof may vary widely.
The stacking state of an organic compound is determined by a polymorph of the compound. That is, the polymorph of the compound determines an electronic state, particularly a perturbation of .pi. electron of the compound. Therefore, the polymorph of the compound is an important factor for improving electronic properties of an organic photoconductive material.
With reference to the technical background, energetic research and development of a novel photoconductive substance, and a novel polymorph thereof are conducted for achieving a high-performance charge generating material. For example, a charge generating material excellent in stability and durability of photoresponse, and shows middle to high photoresponse, which is suitable for short wavelength irradiation of light emitting diode (LED) or for an OPC of a colour laser beam printing machine (LBP), is desired.
A phthalocyanine compound is typical photoconductive substance. Hydroxyaluminium Pc, and hydroxygallium Pc, various polymorphs thereof for example has been investigated, and are practically applied to an electrophotographic photoreceptor. For example, Japanese Patent Kokai Publication No. 93150/1993 describes hydroxyaluminium Pc having a specific polymorph. Japanese Patent Kokai Publication No. 214415/1994 describes some kinds of hydroxymetal Pc. Japanese Patent Kokai Publication No. 501760/1985 describes hydroxyaluminium Pc having a specific XRD Bragg angle in which green absorption is decreased.
Japanese Patent Kokai Publication Nos. 249716/1993, 263007/1993, 279591/1993, 53892/1995, and 67946/1998 describe a novel polymorph of hydroxygallium Pc.
Journal of Japanese Chemical Society "Chemistry and Industrial Chemistry", 1997, No. 12, pages 887 to 898, YAMASAKI Yasuhiro et al, describes .mu.-oxo-metal (Al, Ga In) Pc dimer as a charge generating material (CG material) with respect to alignment thereof in a polymorph, or to the method for making it sensitive to short wavelength irradiation.
Japanese Patent Kokai Publication Nos. 362653/1992, and 184452/1992 describe an electrophotographic photoreceptor, and a coating liquid therefor which contain a .mu.-oxo-metal (III, IV) Pc derivative. Japanese Patent Kokai Publication Nos. 217020/1997, and 88023/1998 describe .mu.-oxo-aluminum Pc dimer, and .mu.-oxo-gallium Pc dimer, each having a specific polymorph. Japanese Patent Kokai Publication No. 295259/1995 describes alkoxy crosslinked metal Pc dimer.